Leveling 85-90: best spec/demon?

I leveled my main (spriest) first to 90, then shaman, paladin, hunter... now thought it was time to level my lock. I kinda love demonology, other spec is destruction (which I haven't played since... july!), I'm using my wrathguard, it goes kinda easy, but every 2-3 fights I need to heal it (health funnel), and I was wondering if it was normal?

I just hit 89 on my lock and I've been Affliction since level 10 and I love it. I'm using the Voidwalker and I have to heal him often but it's very easy because I just pull a ton of mobs and multidot and DS the low health ones. I always have an abundance of shards, things die fast and my pet never dies.

For jade forest affliction is best. Mobs there have low hp so affliction kills them fast. After that you can continue as affliction or go demo both are good with void lord. Or regular void walker but void lord is really solid.

While Affliction really is a ridiculously easy way to level up, it's completely fine if you're in love with Demonology. Just use the Glyph of Demon Hunting, and chain-pull. Make sure to use your Felguard/Wrathguard and not the Void Lord, though. Your demon's cleaves/AoE make short work of big packs, and you shouldn't really have a need for a demon to tank for you.

I've used all the specs for a level (still only 88) but so far they all seem to work fine. I do like afflic with voidlord though because he never runs out of health and its easy to just bring your dots from one mob to the next.

I enjoyed leveling as destruction up to lvl 89. Sacrificed my pet and was able to two-shot mobs regularly with chaosbolt and shadowburn. However this requires good gear to start of at lvl 85 and as soon as i entered the Dreadwastes mobs had to much hitpoints and i switched to affliction (again specced into GoSac). This seemed the fastest way to me and i was able to achieve server-first lvl 90 warlock by mostly questing alone from lvl 86 to 90.